I dont know of any,unless you have a 67-72 GM truck with "ram horn manifolds",there are shorty headers that "might" bolt up to the stock front pipes,but I think the drivers side oem manifolds on some trucks in that era had a angled "dump" though,and those headers are "straight dump" style..
Others here may know if there are any headers like your asking about for square bodies,I have only had headers once on that era of trucks--they rusted through in less than 3 years,so I went back to stock manifolds..headers always had exhaust leaks at the heads and collectors too..I felt no big gain in HP by having them,really..